Method for separating worn bank notes from a quantity of bank notes in bank note processing machines

Abstract

A method is proposed for separating worn bank notes from a quantity of bank notes in bank note processing machines. A target rate c unfit,0 of bank notes to be separated is prescribed. The bank notes are assessed one after the other. In the process they are counted. Further, the value of at least one physical parameter of each bank note affected by wear is measured during the assessment. The measured value, or a value derived therefrom, of each bank note is compared with a threshold value during the assessment. If the threshold value is exceeded, the bank note in question is separated during the assessment. The separated bank notes are counted during the assessment. The threshold value is adapted after assessing each bank note or after a fixed prescribed number m>>n of bank notes by feedback control. The control parameter is the rate c unfit,i of the bank notes separated up to said bank note, and the set parameter is the threshold value.

What is claimed is: 
     
       1. A method for separating worn bank notes from a quantity n of bank notes in bank note processing machines comprising:
 specifying a target rate c unfit,0  for bank notes to be separated, 
 assessing the n bank notes one after another, 
 counting the n bank notes during the assessment, 
 measuring the value of at least one physical variable of each bank note affected by wear during the assessment, 
 comparison of the measured value, or a value derived therefrom, of each bank note with a threshold value during the assessment, 
 separation of bank notes when the threshold value is exceeded during the assessment, 
 counting the separated bank notes during the assessment, and 
 adjusting the threshold value after assessing each bank note or after each firmly determined number m<<n of bank notes by feedback control, where the control variable is the rate c unfit,i  of the bank notes separated up to said bank note and the set parameter is the threshold value. 
 
     
     
       2. The method according to  claim 1  wherein the optical density is determined in at least one section of each bank note as a physical property. 
     
     
       3. The method according to  claim 2 , wherein the optical density is determined by means of at least one light source and at least one optical sensor. 
     
     
       4. The method according to  claim 3 , wherein the light emitted by the light source and reflected by a bank note and/or transmitted through a bank note is measured using the optical sensor. 
     
     
       5. The method according to  claim 1 , wherein the rate c unfit,i  is calculated from the number of all bank notes assessed preceding said bank note on the one part and from the number of bank notes separated up to said bank note on the other part. 
     
     
       6. The method according to  claim 1 , wherein the rate c unfit,i  is calculated as a mean from the rates of the preceding bank notes. 
     
     
       7. The method according to  claim 1 , wherein the control is an adaptive control. 
     
     
       8. The method according to  claim 1 , wherein the control is a fuzzy control. 
     
     
       9. The method according to  claim 1 , wherein, when calculating the threshold value, the sum of the difference from the rate c unfit,0  and c unfit,i  is minimized. 
     
     
       10. The method according to  claim 1 , wherein an IIR filter is used to calculate the threshold value and/or the rate c unfit,i . 
     
     
       11. The method according to  claim 1 , wherein a Kalman filter is used to calculate the threshold value and/or the rate c unfit,i . 
     
     
       12. The method according to  claim 1 , wherein an interval is specified for the threshold value. 
     
     
       13. The method according to  claim 1 , wherein several target rates c unfit,0  are specified and wherein during assessment of the bank notes a switch is made from one target rate to another. 
     
     
       14. A method for separating worn bank notes from a plurality of bank notes in a bank note processing machine comprising:
 specifying a target rate for separating the worn bank notes from the plurality of bank notes; 
 assessing each one of the plurality of bank notes individually and sequentially; 
 counting the plurality of bank notes during the assessing of the plurality of bank notes; 
 measuring, during the assessing, a value of at least one physical variable of each one of the plurality of bank notes; 
 comparing the measured value, or a derivative thereof, of each one of the plurality of bank notes with a threshold value during the assessment; 
 separating from the plurality of bank notes, worn bank notes in which the measured value thereof exceeds the threshold value; 
 counting the separated worn bank notes during the assessing of the plurality of bank notes; and 
 modifying the threshold value each time one of the plurality of bank notes is assessed, or after a subgroup of the plurality of bank notes is assessed, by feedback control; 
 wherein a control variable of the feedback control is a rate of previously separated worn bank notes from the plurality of bank notes. 
 
     
     
       15. The method of  claim 14 , wherein measuring the value of at least one physical variable of each one of the plurality of bank notes includes measuring optical density. 
     
     
       16. The method of  claim 15 , further comprising measuring the optical density with at least one light source and at least one optical sensor. 
     
     
       17. The method of  claim 16 , further comprising measuring with the optical sensor light emitted by the light source and reflected by, and/or transmitted through, a bank note of the plurality of bank notes being measured. 
     
     
       18. The method of  claim 14 , wherein the rate is calculated based on both a number of worn bank notes previously separated from the plurality of bank notes, and a total number of the plurality of bank notes previously assessed. 
     
     
       19. The method of  claim 14 , further comprising calculating at least one of the threshold value and the rate with an IIR filter. 
     
     
       20. The method of  claim 14 , further comprising calculating at least one of the threshold value and the rate with a Kalman filter.